I have a semi-complex situation for my checkout needs. I currently do not have a cart set up at all and have only been taking orders by phone or email. Issues: 1) Some of my clients are tax exempt, others are not. 2) I want to offer net-30 terms to customers who have been approved for credit terms. For approved customers, I want it to go straight through. For new customers, I want them to have the option of choosing net-30 and at the same time including their credit approval form. I want this as least invasive as possible (ie. no passwords, login info, etc). 3) I have a fairly complex volume discount system. Clients can order one product at a time, or they can order cases at a time at discounts. Can this be done with google checkout / zen / oscommerce or is this a custom job?
all check out software is customizable and instead Google check out ,Paypal I believe is reliable in here and you can use http://forums.oscommerce.com/ to learn first the tip and tricks how to play well with the applications